This is just Oda throwing another bone because he loves to protect the legends’ image that much. None of the BBP went all-out especially Shiryu and Kuzan. Y’all would look silly once we see their full arsenal.
Kuzan straight up lied to Teach saying he wanted to kill Garp. Obviously, it would have been stupid to describe how things really were, he managed to gain Teach's trust, he isn't going to throw it away. Garp repeatedly called him out on wavering.
When Aokiji goes full power, Punk Hazard happens and the magma man receives permanent scars.
But yeah, old Garp ~ or <= Aokiji, my guy:saden:
Folks better focus on protecting their Prime Garp > C3 agenda, lord knows it needs protecting when Kuzan can go punch for punch with The Fist:saden: